JP2647848B2 - Concrete admixture - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to admixtures for cement or cement blends, and more particularly to the workability of concrete, mortar or paste which is a hydraulic cement blend. The present invention relates to a concrete admixture capable of preventing deterioration due to cracks and improving its workability and workability.

[Conventional technology]

Conventionally, a cement composition comprising a mixture of cement, water, sand, gravel, and an admixture (admixture), after kneading, the physical and chemical agglomeration of the cement particles progresses with the lapse of time. The amount of entrained air inside decreases, the fluidity gradually decreases, and the workability and workability decrease over time.
For this reason, the cement compound can be used for the workable time (usable time)
Is limited.

In addition, the cement mixture is often transported to the casting site by an agitator truck (mixed concrete mixer truck) after kneading, and the transport time varies greatly depending on the transport distance or traffic congestion. For this reason, at the casting site, the fluidity differs for each agitator vehicle, and it is extremely difficult to obtain constant workability.

In addition, during the pumping of the cement compound, the pumping was temporarily suspended due to lunch break or setup change, etc.
Thereafter, when the pumping is to be resumed, there are many problems such as the fluidity of the cement compound in the pipe being reduced, the workability being remarkably reduced, and the pumping pressure at the time of resuming the pumping rapidly rising or being clogged.

In order to solve these problems, various methods for preventing a decrease in workability of a cement composition have been conventionally devised.

For example, there is a method of adding a curing retarder such as oxycarboxylic acid for the purpose of preventing chemical aggregation. In this method, it is difficult to prevent physical agglomeration even if the hydration reaction of the cement can be delayed, and therefore, slump loss has not yet been prevented. Further, disadvantages such as a decrease in early strength of concrete and mortar occur.

Also, there is a method of preventing slump loss by granulating a concrete fluidizing agent such as β-NSF and adding the granulated fluidizing agent to concrete or the like, and gradually dissolving the granular fluidizing agent (JP-A-54-139929). ). Although this method can prevent slump loss to some extent, it has disadvantages such as a decrease in strength and durability due to the localization of the granular fluidizing agent in the hardened concrete.

There is also a method of maintaining the fluidity of concrete for a long time by adding a fluidizing agent such as β-NSF to the concrete or the like in a divided or continuous manner (Japanese Patent Publication No. 51-15856). Although this method is effective as a method for preventing slump loss, it takes time to add a fluidizing agent,
It is not possible to prevent slump loss of concrete in a situation where it is difficult to add a fluidizing agent, such as concrete in a pumping pipe or concrete in a centrifugal compaction formwork.

As described above, these conventional methods for preventing a decrease in the workability of a cement composition have not a few problems and cannot be said to be satisfactory.

[Means for solving the problem]

The present invention has been made to improve the disadvantages of the above-mentioned conventional method, and a concrete admixture comprising a solution obtained by dissolving a polymer or copolymer of a specific acid anhydride in a non-aqueous solvent is used to improve the workability of a cement compound. -It has been found that workability can be improved, and the present invention has been completed.

That is, the present invention relates to a copolymer of an ethylenically unsaturated dicarboxylic acid anhydride polymer having an average molecular weight of 500 to 50,000 or another polymerizable monomer copolymerizable with the ethylenically unsaturated dicarboxylic acid anhydride. A liquid concrete admixture characterized by a solution of one or more polymers dissolved in a non-aqueous solvent.It is a concrete that is extremely effective in maintaining the fluidity of cement compounds for a long time and preventing slump loss. It is an admixture.

The mechanism of slump loss prevention according to the present invention is presumed as follows.

That is, a cement composition comprising a mixture of cement, water, and, if necessary, sand, gravel, and an admixture (agent) is kneaded, and then chemically aggregated by a hydration reaction of cement particles and physically aggregated by interparticle attraction. Agglomeration proceeds and loses fluidity. For this reason, slump loss occurs in cement compounds such as concrete and mortar. Therefore, if the aggregate of cement particles is redispersed with a cement dispersant, the fluidity of the cement composition is temporarily restored. However, the hydration reaction of cement proceeds further, and a gel of ettringite (commonly called cement bacillus or calcium sulfoaluminate) is continuously produced. As a result, the fluidity of the system continues to decrease and the cement dispersant is adsorbed or stored in the solution and in new precipitated minerals such as ettringite newly formed on the cement particles, and the concentration of the cement dispersant in the solution decreases. Then, the aggregation of the cement particles proceeds. Here, slump loss can be prevented if the cement dispersant can be continuously supplied by any method.

Therefore, the present inventors have proposed a polymer of an ethylenically unsaturated dicarboxylic acid generally known as a dispersant for an inorganic powder, or a copolymer with another polymerizable monomer copolymerizable with an ethylenically unsaturated dicarboxylic acid. Paying attention to water-soluble salts, an attempt was made to gradually release a water-insoluble acid anhydride, which is a precursor of these polymers or copolymers, in a cement composition.

In other words, a water-soluble salt functions as a dispersing agent at the same time as addition and has no sustained release property, but if it is an acid anhydride, it is gradually hydrolyzed by metal ions such as Ca, Na, K, and Mg in the cement composition. Thus, a water-soluble salt having dispersibility can be continuously supplied.

However, a polymer of an anhydride of an ethylenically unsaturated dicarboxylic acid or a copolymer of another polymerizable monomer copolymerizable with an anhydride of an ethylenically unsaturated dicarboxylic acid is hydrolyzed to form a water-soluble salt. To do so, a reaction time of several hours to several tens of hours under a strong alkaline high temperature is required. PH in cement formulation
Is about 12 to 13, and under the condition of about 20 ° C. to 30 ° C., the progress of the hydrolysis reaction is slight. Therefore, a solution of an ethylenically unsaturated dicarboxylic acid anhydride polymer or an ethylenically unsaturated dicarboxylic acid anhydride copolymer with another polymerizable monomer copolymerizable with a non-aqueous solvent is used. It is presumed that the hydrolysis area gradually progresses by increasing the contact area with the alkali in the cement composition, the dispersant is gradually released, and the slump loss of the cement composition can be prevented. .

The average molecular weight of the polymer or copolymer in the present invention is 50
About 0 to 50,000 is desirable, and if the average molecular weight is smaller than this range, the dispersing ability is insufficient, and if the average molecular weight is larger than this range, the effect as a flocculant becomes larger than as a dispersant, and the slump loss prevention effect Is not shown.

The average molecular weight of the polymer or copolymer used in the present invention indicates a weight average molecular weight determined by aqueous gel permission chromatography using polystyrenesulfonic acid as a reference substance.

As the anhydride of the ethylenically unsaturated dicarboxylic acid as a raw material of the polymer or copolymer of the present invention, maleic anhydride,
Examples include itaconic anhydride and citraconic anhydride.

The other polymerizable monomer copolymerizable with the anhydride of the ethylenically unsaturated dicarboxylic acid, which is a raw material of the copolymer of the present invention, is preferably a vinyl polymerizable monomer. Specific examples include olefins, styrene derivatives, acrylic acid, acrylates, allyl alcohol, allyl esters, vinyl ethers, and the like. Desirable are olefins having 2 to 8 carbon atoms and styrene.

Examples of the non-aqueous solvent in the present invention include hydrocarbon, halogenated hydrocarbon, alcohol, phenol, ether, aldehyde, acetal, ketone, nitrogen-containing, and sulfur compound solvents. Although any solvent can be used as long as it can dissolve the polymer or copolymer in the present invention, dimethylformamide and dimethylsulfoxide are preferred.

The concentration of the non-aqueous solvent solution of the polymer or copolymer according to the present invention is not particularly limited, but is preferably about 1 to 20% by weight.

Further, the non-aqueous solvent solution of the polymer or copolymer according to the present invention is a naphthalene sulfonic acid formaldehyde high condensate-based water reducing agent, a sulfonated melamine resin-based water reducing agent, a lignin sulfonic acid-based water reducing agent, and a polycarboxylic acid-based water reducing agent. It can be used in combination with one or more water reducing agents selected from the group consisting of:

The method of adding the concrete admixture of the present invention to the cement composition includes a method of dissolving in the kneading water and an addition to the cement composition once kneaded. When a water reducing agent is used in combination, a naphthalenesulfonic acid formaldehyde high condensate-based water reducing agent, a sulfonated melamine resin-based water reducing agent,
A lignin sulfonic acid-based water reducing agent, a water reducing agent such as a polycarboxylic acid-based water reducing agent and a polyol-based water reducing agent, and a non-aqueous solvent solution of the polymer or copolymer according to the present invention may be previously mixed, Alternatively, one may be mixed with cement or one may be mixed with cement and kneaded before mixing the other.

Further, it can be used in combination with other cement additives (agents), for example, an air entraining agent, a fluidizing agent, a waterproofing agent, an inflating agent (agent), glass fiber, steel fiber, fly ash, blast furnace slag, and the like.

The concrete containing the concrete admixture according to the present invention can be hardened by a method of hardening ordinary concrete, and can be hardened by using a method such as steam curing or autoclave curing.

〔The invention's effect〕

The most significant effect of the use of the concrete admixture according to the present invention is that the fluidity of the concrete can be increased and the fluidity can be kept constant. The present application discloses for the first time in the present invention that the fluidity can be increased and the fluidity can be kept constant by simply performing the above procedure. As described above, it is possible to provide concrete having such a characteristic performance with a polymer of an anhydride of an ethylenically unsaturated dicarboxylic acid or an anhydride of an ethylenically unsaturated dicarboxylic acid having an average molecular weight of 500 to 50,000. Concrete admixture alone containing one or more copolymers with other copolymerizable polymerizable monomers in a non-aqueous solvent, and naphthalenesulfonic acid formaldehyde high condensate-based water reducing agent, sulfonation It becomes possible only by using a concrete admixture that is used in combination with one or more water reducing agents selected from melamine resin water reducing agents, lignin sulfonic acid water reducing agents, and polycarboxylic acid water reducing agents. .

The addition amount of the cement formulation of admixture of the present invention is usually a cement formulation 1 m ³ per 10G～10kg.

The concrete admixture according to the present invention is specifically used for various applications, since the present invention has made it possible to increase the flowability of concrete and to keep the flowability constant. For example, it is used as a pumping aid for concrete. Cement compounds are often cast by pumping, but as mentioned above, when pumping is temporarily suspended due to work lunch breaks, setup changes, mechanical failures, etc. The fluidity of the concrete in the pumping pipe decreases, and the pumping pressure at the time of restarting pumping suddenly rises or a problem such as blockage occurs.

However, when the concrete admixture according to the present invention is added, the fluidity of the concrete is kept constant, the decrease in the fluidity is prevented, and after the pumping is interrupted, the pumping pressure when pumping resumes can be prevented from increasing. Thus, the efficiency of the pumping operation can be significantly increased.

In addition, other agents can be used as centrifugal compaction aids. The centrifugal compaction molding method uses a centrifugal force generated by rotating cement-containing substances such as mortar, concrete, and asbestos-cement mixture to form a secondary cement product.
Although it is a manufacturing method, when centrifugal compaction molding is performed using the concrete admixture according to the present invention, the fluidity of the concrete before molding can be maintained for a long time, so that the product finish becomes easy, and generation of slag is prevented, Effective for clarification of wastewater.

Further examples include cement milk or mortar grouting aids, cement compounds cast by tremy tubes, underwater concrete, concrete for continuous underground walls, etc. It is also effective.

〔Example〕

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

Example 1 A solution was prepared using dimethylformamide or dimethylsulfoxide as a solvent and a copolymer using maleic anhydride as an anhydride of an ethylenically unsaturated dicarboxylic acid and isobutylene as a copolymerizable polymerizable monomer. . Further, in order to examine the effect of the molecular weight, the copolymer solutions having different average molecular weights as shown in Table 2 were prepared.

Using these as concrete admixtures, the fluidity of concrete and the effect of preventing the decrease in fluidity were examined.

The fluidity of concrete and the effect of preventing the decrease in fluidity were measured using the following materials and mixes of concrete.
A 1101 slump test was performed.

<Materials> Cement (C): ordinary Portland cement (specific gravity: 3.1
7) Fine bone (S): from Kinokawa (specific gravity; 2.57) Coarse bone (G): from Hidakagawa (specific gravity; 2.59) <Formulation> Table 1 shows the results.

The amount of the prepared admixture is 0.2% by weight of cement
It is.

A predetermined admixture is put into concrete kneaded based on the formulation shown in Table 1 (50 concretes are kneaded for 2 minutes using a 100-tilt mixer), and slumped at a predetermined time while agitating at a constant speed of 4 rpm. Was measured.

 Table 2 shows the results.

The admixture used here was made into a solution by adding 9 parts by weight of a solvent to 1 part by weight of an isobutylene / maleic anhydride copolymer.

As is clear from the experimental results shown in Table 2, in the experiments Nos. 4 and 6 using the product of the present invention, the slump of concrete was 15 to 16 cm.
And a value almost the same after 90 minutes has passed, and the fluidizing effect and the slump loss preventing effect are extremely excellent. On the other hand, in Experiment No. 2 in which a lump having a particle size of 2 mm was used without forming a solution, neither a fluidization effect immediately after kneading nor a slump loss prevention effect was recognized.

In Experiment No. 3 having a low average molecular weight, neither fluidization effect nor slump loss prevention effect was observed immediately after kneading, whereas in Experiment No. 5 having a high average molecular weight, the effect as a flocculant appeared immediately after kneading. Slump loss has also increased significantly.

Example 2 The copolymer of isobutylene and maleic anhydride used in Example 1 was made into a solution using dimethylformamide, and a naphthalenesulfonic acid-formaldehyde high condensate-based water reducing agent and a sulfonated melamine resin-based water reducing agent were used. Alternatively, the effect of the mixture with the ligninsulfonic acid-based water reducing agent on the prevention of a decrease in the fluidity of concrete was examined by the following method.

 The results are shown in Table-3.

<Experimental method> The time-dependent change of the concrete slump was measured in the same manner as in Example 1.

 The following cement admixtures were used.

(A) Naphthalene sulfonic acid formaldehyde high condensate water reducer (b) Sulfonated melamine resin water reducer (c) Lignin sulfonic acid water reducer (d) Naphthalene sulfonic acid formaldehyde high condensate water reducer A mixture of 50 parts by weight of a solution (10% by weight) of an isobutylene / maleic anhydride copolymer dissolved in dimethylformamide.

(E) A mixture of 50 parts by weight of a sulfonated melamine resin water reducing agent and 50 parts by weight of a solution (10% by weight) of an isobutylene / maleic anhydride copolymer dissolved in dimethylformamide.

(F) A mixture of 50 parts by weight of a ligninsulfonic acid-based water reducing agent and 50 parts by weight of a solution (10% by weight) of a solution of isobutylene / maleic anhydride copolymer in dimethylformamide.

The isobutylene / maleic anhydride copolymers (d), (e) and (f) used had the average molecular weight of 10,000 used in Example 1, and dimethylformamide was used as a solvent.

As is clear from the experimental results shown in Table 3, the concrete slump was 90% in Experiment Nos. 10 to 12 using the product of the present invention.
It could be kept almost constant for a minute. On the other hand, experiment N used for comparison
In o.7 to 9, the slump of concrete decreases with time, and no slump loss preventing effect is observed.

Claims (4)

(57) [Claims] A copolymer of an ethylenically unsaturated dicarboxylic acid anhydride polymer having an average molecular weight of 500 to 50,000 or another polymerizable monomer copolymerizable with an ethylenically unsaturated dicarboxylic acid anhydride. A liquid concrete admixture comprising a solution in which one or more of the coalesced substances are dissolved in a non-aqueous solvent. 2. The concrete admixture according to claim 1, wherein the other polymerizable monomer copolymerizable with the anhydride of the ethylenically unsaturated dicarboxylic acid is a vinyl polymerizable monomer. 3. The concrete admixture according to claim 1, wherein the other polymerizable monomer copolymerizable with the anhydride of the ethylenically unsaturated dicarboxylic acid is an olefin having 2 to 8 carbon atoms. 4. The non-aqueous solvent is dimethylformamide or / and / or
The concrete admixture according to any one of claims 1 to 3, wherein the admixture is dimethyl sulfoxide.